After F. Scott Fitzgerald married Zelda Sayre, they moved to the East Coast, an area that he found decadent and materialistic. While he and his wife revelled in the company of the wealthy, they often offended them. For, his background somewhat contributed to his resentment of the frivolous and extravagant as one side of his family looked down upon the other.
In his novel The Great Gatsby, Fitzgerald depicts the amorality and materialism of the very wealthy who are also very socially conscious such as Daisy and Tom Buchanan and the couple, the Sloanes, who pretend that they want Gatsby to join them as they ride their horses.
Some people can get away with things because of wealth. It is also not just wealth, but family status, that make people think they can do whatever they want. Sometimes people look the other way because of the family the no-gooder is from.
We can see some hollowness or shallowness in the characters who attend Gatsby's parties.
We can also see some "exceptionalism" on Tom's part as he espouses his racist theories early on and later treats Myrtle poorly (along with her husband) without any compunction or regret.
For Tom, who comes from "old money", we can see his behavior as being influenced by his position and his status. Arguably, he is capable of acting badly becuase he is completely secure in his wealth.
For the party-goers, we may argue that their behavior is bad because they are prepared to both glorify and deride the great wealth of the host; to praise the quality of the rug while they grind mud into it and spill their drinks.